Replacement and repair of instantaneous internal gas hot water systems

internal gas hot water system repair

Inside gas hot water systems.

While not as common as outdoor gas hot water heaters, internal instantaneous gas hot water systems can still be found in older houses and apartment buildings throughout Sydney.  It is extremely important that indoor gas hot water heaters are installed correctly with a double skin flue that exhausts any carbon monoxide fumes safely to the outside of the property.

Indoor gas hot water heater regulations.

We were contacted recently by a customer in Liverpool (Western Sydney), whose internal gas hot water system had started leaking.  Once onsite, we could see that the flue attached to the old instantaneous gas hot water system terminated in the roof space.  This is no longer legal.

The flues attached to inside gas hot water systems must exhaust to the outside of the property – not into the roof space.

Additionally, flues must now be double insulated.  The flue at this Liverpool property was only single skin.

Single skin flues get extremely hot and, are not only dangerous to touch, but can be a serious fire hazard.  Double insulated flues are cool to the touch – similar to a double insulated glass or coffee cup.

Once our hot water specialist John arrived onsite at the Liverpool property, he explained to the customer the regulatory requirements surrounding indoor gas hot water systems and what was required to ensure their heater complied. The customer was more than happy for us to undertake whatever changes were required to make the hot water system safe.

indoor gas hot water system repair

Instantaneous gas hot water system repair.

Next, John had to determine why the old instantaneous hot water heater was leaking.  As John suspected, there were multiple problems with the old hot water system that, unfortunately, made it uneconomical to repair.  A replacement hot water system would need to be installed.  Unfortunately, parts are often no longer manufactured for many old hot water systems, rendering them impossible to fix. If parts are available, they may have to be shipped from overseas causing extensive delays to the repair process.  For obvious reasons, most customers are not happy to go without hot water whilst waiting for spare parts to arrive.

John discussed the replacement hot water heater options available, taking into consideration the customer’s budget and hot water usage requirements, and recommended the Bosch Gas ci 10 Hydropower internal instantaneous hot water system.  The customer was happy with this recommendation and John proceeded to remove the old hot water system and install the new one in the same location.

Next, the old, single skin flue was removed and replaced with a compliant, double insulated flue (double skin flue).  Instead of the flue terminating the roof space, John carried it out through the roof and into the fresh air above the property.  Refer to the photo below.

The customer now has a new internal gas hot water system that is safe and complies with current regulations, offering them peace of mind and years of trouble-free hot water usage.

A breakdown of this gas hot water system replacement job is as follows: 

  • Attend the Liverpool property to inspect and repair the old indoor gas hot water system.
  • Assess the site for safety and take appropriate actions.
  • Inspect the old instantaneous gas hot water system to determine the source of the leak.
  • Determine that the old hot water system was beyond economical repair.
  • Discuss with the customer replacement internal gas hot water system models.
  • Supply and install new Bosch Gas ci 10 Hydropower internal instantaneous hot water system back in the same location.
  • Remove old, single skin flue.
  • Supply and install new double insulated flue (twin skin). Extend the new flue beyond the roof.
  • Install dektite flashiongs 100mm.
  • Install twin skin flue cowl to suit twin skin flue.
  • Install twin skin disconnector joiner.
  • Adjust and recommend the new hot water system to the hot and cold pipework.
  • Commission and test the new instantaneous hot water system.
  • Clean up the site and remove any associated rubbish.
  • Recycle old hot water system.

Move / replace indoor gas hot water heater with outdoor system.

We are sometimes asked by customers to disconnect and remove their indoor gas hot water system and replace it with a new heater outside. This is certainly possible and just one of the services we provide.

To move the hot water system, first, we disconnect the old heater located inside the house. The existing pipework has to be decommissioned and made safe.

Next, we discussed with the customer their household hot water usage requirements so we could supply them with a new system that would accommodate their hot water usage needs now and in the future.

Next, we install new pipework that will connect the outdoor hot water system to the electricity / gas supply and hot / cold water supply. Sometimes a concrete slab may need to be installed to support the hot water system in its new location outside.

Once complete, the customer should be back enjoying hot water within a couple of hours.


Hot water is our business, it’s not a sideline, and each year we repair and install hundreds of hot water systems in homes and businesses across all Sydney suburbs. Our fully qualified, licensed hot water heater installers have over 25+ years of experience each. We are fully insured and pride ourselves on our customers with old-fashioned customer service they can rely on.

We are accredited service agents for all the hot water heater brands including RheemDuxRinnaiAquamaxBoschConergyHockingApricusVulcanEdwards SolarSolahartEverhot and more.

We are qualified to undertake all the plumbing and electrical work required to install a new hot water system so you don’t waste time and money employing multiple trades.

Best of all, we have all the equipment needed to install your hot water system today. We don’t have to hire or wait for other trades to arrive with the required equipment.

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